George Leonard wrote a lovely little book called Mastery. The key takeaway from this book is to "learn to love the plateau". The path to Mastery is stepped improvement followed by long plateaus. The start of the book has graphs of different kinds of learner such as "the dabbler" and "the perpetual beginner". I think if you follow a deliberate practice regimen and stick to it, you will see improvement; it's just that this improvement won't be continuous. You'll stagnate, even go down in skill from time to time, but sooner or later you'll take another step up.

That’s definitely been my experience. I once got so fed up with a plateau I didn’t touch my classical guitar for about two months and only played electric guitar during that time. When I went back to the classical guess what had happened? I’d improved! It works in strange ways.

I’ve since learned to accept the plateau as part of the learning experience. In fact, I now quite enjoy the challenge of breaking through the next one. I recently made a lot of rapid progress doing micro exercises on open strings or scale fragments. I can feel that progress stalling now so time to come up with some ideas for the next breakthrough.

Interesting suggestion, as it triggers my other thoughts, which may not be relevant to Lare's original topic of "technical plateaus", rather "why has my progress stalled", e.g. mismatched expectations or objectives between a teacher and his/her student?

The teacher will train a student to various levels of objectives, from recreational -for old(er) guys like me, to professional classical guitarists. As such, different methodologies may apply to guide and motivate a student. Otherwise, the general complaint is something like "the student is not ready for next fun/challenging exercises" from a teacher and/or "taking lessons is like pulling teeth" from a student?!

So it may not be directly a technical plateau as a result of lack of interest or motivation, but the effect is the same, stalled progress.

Thus changing a teacher, now with a more defined objective(s) and perhaps a custom curricular learning plan would help.